turkish lessons

The 3 Spelling Variations of the Suffix 'den' ( from )are : 'dan', 'ten', and 'tan'
This isn't as mysterious as it may first seem. The Turkish language always strives for a harmonious sound,it's not such an horrific task to cater for these minor spelling variations.
So before you set about attaching 'den' to an attachee word you need to be conscious of two points.
Firstly, if the attachee word ends in ç, f, h, k, p, s, ş, t then the 'd' in 'den' must change into 't' before the attachment takes place. Secondly, the 'e' in 'den' (or 'ten') may have to change to 'a' depending on the last vowel in the attachee word -- in accordance with the Rule of Vowel Harmony.
Here is an example with the 'den' suffix and each of its spelling variants:
( how can we say"from Istanbul" in Turkish? )

İstanbul
1. attachee word: ç, f, h, k, p, s, ş, t? NO !
2.So,should 'd' of the suffix change to 't' ? NO !
3.Observe the last vowel of the attachee word.

What does the Rule of Vowel Harmony dictate?
Should 'e' of the suffix change to 'a' ? YES !
and...
Resulting Turkish :İstanbul'dan
English Meaning :from Istanbul
Rule of Turkish Vowel Harmony a ...may be followed by... a or ı
ı ...may be followed by... a or ı
o ...may be followed by... u or a
u ...may be followed by... u or a
e ...may be followed by... e or i
i ...may be followed by... e or i
ö ...may be followed by... ü or e
ü ...may be followed by... ü or e

(phew !!!) want to try these examples ?
from Eskişehir : ......?
from Muş : .............?
from Gaziantep : .....?

yeah !!!